Improvement in resonant charging circuit

ABSTRACT

A resonant charging choke and switching arrangement in a regulator for controlling the voltage across a capacitive storage element despite large variations in the voltage of a source of DC power for such element, the switching arrangement being operated through a control circuit: (a) electrically to disconnect the resonant charging choke from the capacitive storage element; and, (b) electrically to connect the resonant charging choke, through a low impedance circuit to the source of DC power when the voltage across the capacitive storage element reaches a predetermined level.

O Umted States Patent 1151 3,675,116 Israel July 4, 1972 541 RESONANTCHARGING CIRCUIT 3,486,043 12/1969 .lohannessen ..307/265 3,139,5856/1964 Ross et a1 ..328/67 X 3,013,165 12/1961 Bataille ..307 108 I 1lnvemorl 15ml,1/56,WYSter,MaSS- 3,363,184 1/1968 Smith "328/67 x 73 A1.R th C L t M I wgnee 8y eon ompany exmg ass Primary Examiner-A. D.Pellinen Filed! March 15,1971 Attorney-Philip J. McFarland, Joseph D.Pannone and [21] Appl' 124,136 Richard M. Sharkansky 57 ABSTRACT [52]U.S.Cl. ..323/17, 307/246, 32342228357, A resonant g g choke andSwitching arrangement in a [5]] Int Cl G05 1/56 regulator forcontrolling the voltage across a capacitive [581 Field 108 246 storageelement despite large variations in the voltage of a 307 323/22 SC i fsource of DC power for such element, the switching arrange- 325/1 328/65ment being operated through a control circuit: (a) electrically todisconnect the resonant charging choke from the capacitive storageelement; and, (b) electrically to connect the resonant [56] ReferencesCited charging choke, through a low impedance circuit to the sourceUNITED STATES PATENTS of DC power when the voltage across the capacitivestorage 3 H9 968 H1964 S h b 328/67 element reachesapredetermlned level.

c on erg 3,333,120 7/ 1967 Tomlin ..307/ 106 1 Claim, 2 Drawing FiguresFROM SYNCHRONIZER 3/ 23 (F161) at $2.155 FIL 29 lF-IG.I) NETWORKl3lFlG- 1) REGULATOR I REQONAN'I CHARGING CIRCUIT BACKGROUND OF THEINVENTION This invention pertains generally to direct current powersupplies and particularly to regulated power supplies of such type.

It is known in the art that any capacitive storage element, as.

a pulse forming network in a radar system, may be periodically chargedfrom a direct current source through a resonant charging choke andswitching arrangement. In applications in which size, weight andefficiency are not limiting factors, any one of many well knownarrangements of such nature operate satisfactorily. That is, if size,weight and efficiency of the regulator is not a limiting factor in, say,a radar system, the capacitive storage element in such a system, as thepulse forming network, may be charged to a precise level at the end ofeach charge cycle of operation by any one of many known regulators.

Unfortunately, however, the size, weight and efficiency of any givenregulator is often of paramount concern in practical radar systems. Forexample, the regulator and switching arrangement in a ground-controlledapproach (GCA) radar for tactical use by the military must be small,light and efficient to make relocation of such a radar as easy aspossible.

A regulator using the resonant charging process is generally providedwith: (a) a switching arrangement between the charging choke of theregulator and the capacitive storage element to be charged; and, (b)means for discharging the remanent energy in the charging choke afterthe capacitive storage element has been charged. According to the art, adiode may be placed in circuit between the charging choke and thecapacitive storage element to operate as a switch. An auxiliary windingon the charging choke may then be arranged to discharge the remanentenergy therefrom and to create a voltage to back bias the diode whencharging of the capacitive storage element is completed. It has beenfound, however, tat practical regulators so constructed do not reduceinput variation by more than I.

SUMMARY OF THE INVENTION Therefore, it is a primary object of thisinvention to provide a power supply incorporating an improved regulatorand charging circuit for a capacitive storage element, as a linemodulator for a power oscillator in a GCA radar, such power supply beingadapted periodically to recharge such storage element to a preciselevel.

Another object of this invention is to provide an improved regulator andcharging circuit operating as hereinbefore stated, such circuitry beinglight in weight, small in size and high in efi'iciency when compared toknown regulators.

Still another object of this invention is to provide an improvedregulator and charging circuit arranged in such a manner that when acapacitive storage element is resonantly charged by such regulator andcharging circuit to a predetermined level, a switching arrangement isautomatically actuated to disconnect the capacitive storage element fromthe regulator and charging circuit and the energy then stored in suchcircuit is quickly removed therefrom.

These and other objects of this invention are attained generally byproviding, in an improved resonant charging choke circuit for acapacitive storage element, a charging choke having a main winding andan auxiliary winding, the main winding being connected in circuit,through appropriate switching arrangements, with a DC power supply andthe capacitive storage element to permit resonant charging of suchstorage element to a predetermined level and the auxiliary winding beingconnected in circuit, through appropriate control circuits, with the DCpower supply to return the remanent energy in the charging choke to theDC power supply as soon as the energy delivered to the capacitivestorage element reaches the predetermined level.

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding ofthis invention reference is now made to the following description of apreferred embodiment of this invention as illustrated in the drawing,wherein:

FIG. 1 is a block diagram, greatly simplified, of a radar systemincorporating the contemplated power supply; and,

FIG. 2 is a schematic drawing showing one embodiment of the improvedregulator portion of the power supply of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, it maybe seen that a pulse radar system incorporating this invention includesapower supply 11, a pulse forming network 13, a power oscillator 15, aduplexer 17, an antenna 19, a receiver/indicator 21 and a synchronizer23. Except as shown in detail in FIG. 2, the various elements of theillustrated system are conventional. Thus, the power supply 11 mayconsist of a power source 25 (say, a three phase AC generator having anoutput which may vary within wide limits), a rectifier 27 and a filter29 ultimately to produce DC power at the input of a regulator 31 (to bedescribed hereinafter). The regulator 31, in turn, resonantly charges tostep up the voltage level of the DC power to a predetermined levelrequired for charging of the pulse forming network 13. The latter, forexample, may be a so-called sofi tube modulator wherein a pulse formingnetwork is charged and discharged through a pulse transformer (notshown) to the power oscillator 15. With a known arrangement of such atype, or any other known modulator, the voltage level of the DC power atthe output of the regulator 31 may be stepped up to the level requiredto operate the power oscillator 15. The latter, for example, may be amagnetron. It has long been appreciated that frequency stability andconstancy of the radio frequency power output of a magnetron requiresthat the voltage and current of the output of the pulse forming networkbe kept substantially the same from pulse to pulse, In order to maintainthe voltage and current out of a pulse fonning network at constantvalues it is, of course, necessary correspondingly to maintain theoutput of the regulator. It has also long been known that it is highlydesirable to have the regulator operate without being affectedappreciably by changes in the pulse repetition frequency of the system.

Referring now to FIG. 2, it may be seen that the regulator 31 showntherein, which meets the just-mentioned requirements, includes a siliconcontrolled rectifier (SCR 35), a charging choke (not numbered) having amain winding 37 disposed to charge resonantly when a voltage is appliedthereto and an isolating diode 39. A conventional voltage divider (notnumbered) but made up of resistors 41, 43 is connected between theisolating diode 39 and ground as shown. For convenience, a capacitivestorage element, as capacitor 33, is also shown connected in parallelwith such voltage divider although it will be recognized that such anelement in practice would be located in the pulse forming network 13 ofFIG. 1. It is evident that at the instant SCR 35 is caused to conduct,as shown here, when a signal from the synchronizer 23 (FIG. I) isapplied to its control electrode, the voltage across the capacitor 33(which is then zero) will cause the isolating diode 39 to be biased intoits conducting state Therefore, the inductive charging of the mainwinding 37 will, in turn, cause current to flow through the isolatingdiode 39 into the capacitor 33 to charge the latter toward a voltagetwice that of the output of the filter 29 (FIG. 1 When capacitor 33 ischarged to its desired voltage level (less than twice the filter outputvoltage), isolating diode 39 ceases to conduct for reasons to be setforth hereinafter.

The level of the voltage across the capacitor 33 is measured at alltimes by sensing the voltage at a tap (not numbered) in the conventionalvoltage divider made up of resistors 41, 43. When the voltage at the tapbecomes equal to a reference voltage from a source 45, i.e., when thecapacitor 33 is charged to the level desired, a difierential amplifier47 is caused to produce a control signal on the control electrode of asilicon controlled rectifier (SCR 49) to turn such element on." Theanode and cathode electrodes of SCR 49 are connected as shown to theinput line (not numbered) of the regulator 31 and to diodes 51, 53. Theformer diode is connected to an auxiliary winding 55 on the chargingchoke, as is conventional, and the latter is connected, via a resistor57 and a capacitor 59, to the main winding 37.

In passing, it will be noted that the turns ratio between the mainwinding 37 and the auxiliary winding 55 may be varied within widelimits. The particular turns ratio used depends, as is known, on thedesired range of regulation for any application.

It will be observed that when SCR 49 is caused to conduct as justdescribed, diodes 51, 53 are then biased to conduct, thereby completingan electrical circuit between each winding of the choke (not numbered),the isolating diode 39 and the filter 29 (FIG. 1). It follows, then,that isolating diode 39 is forced, almost instantaneously, into itsnonconducting state to disconnect, electrically, the capacitor 33 fromthe main winding 37. At the same time diode 53 and diode 51 complete anelectrical path (through SCR 49) back to the filter 29 (FIG. 1) toprovide a discharge path for the energy remaining in the charging choke.When the voltage across diodes 51, 53 drops below their contactvoltages, diodes 51, 53 become nonconducting, thereby causing SCR 35 andSCR 49 to shut off. The regulator 31 is then in condition to operateagain.

It will be observed that the leakage inductance of the charging chokehas no effect on the operation of the just-described regulator. That is,the operation of the isolating diode 39 when the capacitor 33 is chargedto its desire level is controlled by SCR 49 and a suitable network, herecomprising diode 53, resistor 57 and capacitor 59. It will also beobserved that the degree of regulation obtained by use of thejust-described regulator is dependent on the speed at which SCR 49 maybe caused to conduct after a control signal is generated by thedifferential amplifier 47. Still further, it will be noted that, becausethe remanent energy in the charging choke is returned to the filter 29(FIG. 1) through a low impedance path (except for a relatively smallamount dissipated by resistor 57) the efficiency and bandwidth of thedisclosed regulator are high. With a high efficiency, smaller andlighter components become feasible and with a wide bandwidth, and

resulting short switching time, operation with a changing pulserepetition frequency is possible.

Having described one embodiment of this invention, it will be evident toone of skill in the art that modifications may be made without departingfrom any inventive concepts. Thus, it is obvious that either SCR 35 orSCR 49 may be replaced with switching tubes, as hydrogen thyratrons.Further, it is obvious that the control signal for SCR 35 may be passedthrough logic circuitry, including sensing means similar to that shownfor SCR 49, so that operation of SCR 35 may be inhibited when the outputvoltage of the filter 29 (FIG. 1) is outside broad limits. Stillfurther, will be obvious that the circuit elements to back bias theisolating diode 39 may be changed so long as any replacement elementsprovide a path to apply a back bias to the isolating diode 39 as soon asthe capacitor 33 is charged to its desired level. It is felt, therefore,that this invention should not be restricted to its disclosed embodimentbut rather should be limited only by the spirit and scope of theappended claims.

What is claimed is:

1. In an electric power supply utilizing a main winding of a resonantcharging choke and an isolating diode periodically to supply electricpower from a DC power supply to a capacitive storage element, such mainwinding being electrically disconnected from such storage element byoperation of such isolating diode when the level of the voltage acrosssuch storage element equals a predetermined level, the improvementcomprisa. an auxiliary winding coupled to the main winding of theresonant charging choke, one end of such auxiliary windin beinggrounded;

b. a rst normally nonconductive diode in circuit with the second end ofthe auxiliary winding;

c. a second normally nonconductive diode in circuit with the junctionbetween the main winding of the resonant charging choke and theisolating diode; and,

d. switching means, in circuit with the first normally nonconductivediode and the second normally non-conductive diode, such switching meansbring operative when the voltage across the capacitive storage elementreaches its predetermined level to cause the first and the secondnormally non-conductive diodes then to conduct.

1. In an electric power supply utilizing a main winding of a resonantcharging choke and an isolating diode periodically to supply electricpower from a DC power supply to a capacitive storage element, such mainwinding being electrically disconnected from such storage element byoperation of such isolating diode when the level of the voltage acrosssuch storage element equals a predetermined level, the improvementcomprising: a. an auxiliary winding coupled to the main winding of theresonant charging choke, one end of such auxiliary winding beinggrounded; b. a first normally nonconductive diode in circuit with thesecond end of the auxiliary winding; c. a second normally nonconductivediode in circuit with the junction between the main winding of theresonant charging choke and the isolating diode; and, d. switchingmeans, in circuit with the first normally nonconductive diode and thesecond normally non-conductive diode, such switching means bringoperative when the voltage across the capacitive storage element reachesits predetermined level to cause the first and the second normallynon-conductive diodes then to conduct.